Electrode unit, power transmitting device, power receiving device, electronic device, vehicle, and wireless power transmission system

ABSTRACT

An electrode unit for use in a power transmitting device to transfer electric power to an object that is configured to be provided at a first position and at a second position of the power transmitting device and includes a power receiving device to receive electric power from the power transmitting device at the first position and at the second position. The electrode unit includes a first group of electrodes to which a first voltage is applied when power is transmitted and second group of electrodes to which a second voltage is applied when power is transmitted, wherein the second voltage has a phase that is different from a phase of the first voltage by a value greater than 90 degrees and less than 270 degrees.

This is a continuation under 35 USC § 120 of U.S. application Ser. No.16/035,613, filed Jul. 14, 2018, the entire disclosure of which ishereby incorporated herein by reference.

BACKGROUND 1. Technical Field

The present disclosure relates to an electrode unit, a powertransmitting device, a power receiving device, an electronic device, avehicle, and a wireless power transmission system.

2. Description of the Related Art

In recent years, wireless power transmission techniques have beendeveloped for transmitting electric power wirelessly, i.e., in acontactless manner, to devices that are capable of moving or beingmoved, e.g., mobile phones and electric vehicles. The wireless powertransmission techniques include methods based on electromagneticinduction and methods based on electric field coupling. Among these, awireless power transmission system based on the electric field couplingmethod is such that, AC power is transferred wirelessly from a pair ofpower transmitting electrodes to a pair of power receiving electrodes,with the pair of power transmitting electrodes and the pair of powerreceiving electrodes opposing each other. For example, such a wirelesspower transmission system based on the electric field coupling method isused in applications where electric power is transferred to a load froma pair of power transmitting electrodes on or under a road surface or afloor surface. Japanese Laid-Open Patent Publication No. 2010-193692discloses an example of such a wireless power transmission system basedon the electric field coupling method.

SUMMARY

With conventional wireless power transmission based on the electricfield coupling method, an electric field leakage may occur around thepower transmitting electrodes or the power receiving electrodes, therebycausing nearby electronic devices to malfunction. The present disclosureprovides a technique with which it is possible to suppress the electricfield leakage around power transmitting electrodes or power receivingelectrodes.

In order to solve the problem described above, an electrode unitaccording to an embodiment of the present disclosure is:

an electrode unit for use in a power transmitting device or a powerreceiving device of a wireless power transmission system based on anelectric field coupling method, the electrode unit including:

a first group of electrodes including a plurality of first electrodes towhich a first voltage is applied when power is transmitted; and

a second group of electrodes including a plurality of second electrodesto which a second voltage is applied when power is transmitted, whereinthe second voltage has a phase that is different from a phase of thefirst voltage by a value greater than 90 degrees and less than 270degrees, wherein:

the plurality of first electrodes and the plurality of second electrodesare arranged in a first direction along an electrode installationsurface; and

at least two of the plurality of first electrodes and at least two ofthe plurality of second electrodes are arranged alternating with eachother in the first direction.

These general and specific aspects may be implemented using a system, amethod, an integrated circuit, a computer program or a storage medium,or any combination of systems, devices, methods, integrated circuits,computer programs, and storage media.

With the technique of the present disclosure, it is possible to suppressthe electric field leakage around power transmitting electrodes or powerreceiving electrodes, and reduce the risk of causing nearby electronicdevices to malfunction.

These general and specific aspects may be implemented using a system, amethod, and a computer program, and any combination of systems, methods,and computer programs.

Additional benefits and advantages of the disclosed embodiments will beapparent from the specification and Figures. The benefits and/oradvantages may be individually provided by the various embodiments andfeatures of the specification and drawings disclosure, and need not allbe provided in order to obtain one or more of the same.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically showing an example of a wireless powertransmission system based on the electric field coupling method.

FIG. 2 is a diagram showing a general configuration of the wirelesspower transmission system shown in FIG. 1.

FIG. 3 shows an example of the distribution of an electric field formedaround power transmitting electrodes 120 a and 120 b when transmittingpower.

FIG. 4 is a diagram schematically showing a wireless power transmissionsystem according to Embodiment 1 of the present disclosure.

FIG. 5 is a diagram showing a general configuration of the wirelesspower transmission system shown in FIG. 4.

FIG. 6 is a top view schematically showing a configuration example of apower transmitting device.

FIG. 7 is a schematic cross-sectional view illustrating the effect ofsuppressing the leakage electric field.

FIG. 8A is a top view schematically showing an example in which thepower transmitting device includes two first power transmittingelectrodes 120 a and two second power transmitting electrodes 120 b.

FIG. 8B is a top view schematically showing an example in which thepower transmitting device includes three first power transmittingelectrodes 120 a and two second power transmitting electrodes 120 btherebetween.

FIG. 8C is a top view schematically showing the power transmittingdevice includes three first power transmitting electrodes 120 a andthree second power transmitting electrodes 120 b.

FIG. 9 is a top view schematically showing an example of a configurationin which two third electrodes 520 are arranged on opposite sides of agroup of power transmitting electrodes.

FIG. 10 is a cross-sectional view schematically showing the effect ofthe third electrodes 520.

FIG. 11A is a diagram schematically showing an example of aconfiguration in which two third electrodes 520 are connected to eachother.

FIG. 11B is a diagram schematically showing another example of aconfiguration in which two third electrodes 520 are connected together.

FIG. 12 is a graph showing the change of the leakage electric fieldsuppressing effect with respect to the number of pieces into which anelectrode is divided and the presence/absence of the third electrode.

FIG. 13A is a top view schematically showing an example of aconfiguration in which power transmitting electrodes 120 a and 120 blocated at opposite sides have a smaller width than that of powertransmitting electrodes 120 a and 120 b located on the inner side.

FIG. 13B is a cross-sectional view schematically showing an example ofan electric field produced from a group of power transmitting electrodesof the configuration shown in FIG. 13A.

FIG. 14A is a graph showing the change of the size of the risk regionwith respect to the ws/wc ratio.

FIG. 14B is another graph showing the change of the size of the riskregion with respect to the ws/wc ratio.

FIG. 15 is a diagram schematically showing another embodiment.

FIG. 16 is a block diagram generally showing a configuration thatrelates to power transmission of the wireless power transmission system.

FIG. 17 is a circuit diagram showing a more detailed configurationexample of the wireless power transmission system.

FIG. 18A is a diagram schematically showing a configuration example of apower transmitting circuit 110.

FIG. 18B is a diagram schematically showing a configuration example of apower receiving circuit 210.

FIG. 19 is a diagram showing an example of a factory where a pluralityof location detecting marks are arranged on the floor surface.

FIG. 20 is a diagram schematically showing an example of a mobile systemin which power is transmitted and information is read at the same time.

FIG. 21 is a block diagram showing a basic configuration of a systemaccording to Embodiment 2 of the present disclosure.

FIG. 22A is a cross-sectional view schematically showing an example of aconfiguration and an arrangement of a system having an electronicdevice.

FIG. 22B is a cross-sectional view schematically showing another exampleof a configuration and an arrangement of a system having an electronicdevice.

FIG. 23 is a diagram showing a variation of the configuration of FIG.22.

FIG. 24A is a diagram showing an example of a configuration of atransparent region of a power receiving electrode.

FIG. 24B is a diagram showing another example of a configuration of atransparent region of a power receiving electrode.

FIG. 25 is a diagram showing an example of a configuration in which ablocking member includes a shield having an aperture therein.

FIG. 26 is a diagram showing another example of a shield.

FIG. 27 is a diagram showing a variation of the configuration shown inFIG. 25.

FIG. 28 is a diagram showing another variation of the configurationshown in FIG. 25.

FIG. 29 is a diagram showing an example of a vehicle including a sensorfor detecting humans.

FIG. 30 is a diagram showing a general configuration of a sensor.

DETAILED DESCRIPTION Findings which are Basis of Present Disclosure

Findings which are the basis of the present disclosure will be describedbefore describing embodiments of the present disclosure.

FIG. 1 is a diagram schematically showing an example of a wireless powertransmission system based on the electric field coupling method. The“electric field coupling method” refers to a method of powertransmission in which electric power is wirelessly transmitted from agroup of power transmitting electrodes including a plurality of powertransmitting electrodes to a group of power receiving electrodesincluding a plurality of power receiving electrodes via an electricfield coupling (hereinafter referred to also as “a capacitive coupling”)between the group of power transmitting electrodes and the group ofpower receiving electrodes. The illustrated wireless power transmissionsystem is a system for wirelessly transmitting electric power to atransport robot 10 such as an automated guided vehicle (AGV) used fortransporting articles inside a factory, for example. In this system, apair of flat plate-shaped power transmitting electrodes 120 a and 120 bare arranged on a floor surface 30. The transport robot 10 includes apair of power receiving electrodes opposing the pair of powertransmitting electrodes 120 a and 120 b. The transport robot 10 uses thepair of power receiving electrodes to receive AC power transmitted fromthe power transmitting electrodes 120 a and 120 b. The received power issupplied to a load of the transport robot 10, such as a motor, asecondary battery or a capacitor for storing electricity. Thus, thetransport robot 10 is driven or charged.

FIG. 1 shows XYZ coordinates representing the X, Y and Z directions thatare orthogonal to each other. The illustrated XYZ coordinates will beused in the following description. The Y direction denotes the directionin which the power transmitting electrodes 120 a and 120 b extend, the Zdirection denotes the direction that is perpendicular to the surface ofthe power transmitting electrodes 120 a and 120 b, and the X directiondenotes the direction perpendicular to the Y direction and the Zdirection. The X direction is the direction in which the powertransmitting electrodes 120 a and 120 b are arranged next to each other.Note that the directions of structures shown in the figures of thepresent application are determined in view of the ease of understandingof the description herein, and they do not in any way limit directionsto be used when actually carrying out any embodiment of the presentdisclosure. Also, the shape and size of the whole or part of anystructure illustrated in the figures do not limit the actual shape andsize thereof.

FIG. 2 is a diagram showing a general configuration of the wirelesspower transmission system shown in FIG. 1. The wireless powertransmission system includes a power transmitting device 100 and thetransport robot 10. The power transmitting device 100 includes the pairof power transmitting electrodes 120 a and 120 b, and the powertransmitting circuit 110 for supplying AC power to the powertransmitting electrodes 120 a and 120 b. The power transmitting circuit110 is an AC output circuit including an inverter circuit, for example.The power transmitting circuit 110 covers the DC power supplied from aDC power supply (not shown) to AC power, and outputs the AC power to thepair of power transmitting electrodes 120 a and 120 b. A matchingcircuit for reducing impedance mismatch may be inserted at a positionpreceding the application of AC-converted power to a power transmittingelectrode.

The transport robot 10 includes a power receiving device 200 and a load330. The power receiving device 200 includes a pair of power receivingelectrodes 220 a and 220 b, and a power receiving circuit 210 forconverting the AC power received by the power receiving electrodes 220 aand 220 b into a type of electric power that is required by the load 330and supplying the converted power to the load 330. The power receivingcircuit 210 may include various circuits such as a rectifier circuit ora frequency conversion circuit, for example. A matching circuit forreducing impedance mismatch may be inserted at a position preceding theoutput of the power received by the power receiving electrode to arectifier circuit.

The load 330 is a component that consumes or stores electric power, suchas a motor, a capacitor for storing electricity or a secondary battery,for example. Electric power is wirelessly transmitted between the pairof power transmitting electrodes 120 a and 120 b and the pair of powerreceiving electrodes 220 a and 220 b, while they oppose each other, viaelectric field coupling therebetween. The transmitted power is suppliedto the load 330.

The power transmitting electrodes may be arranged so as to cross thefloor surface rather than parallel to the floor surface. For example,when installed on a wall, etc., the power transmitting electrodes may bearranged substantially vertical to the floor surface. The powerreceiving electrodes of the vehicle may also be arranged so as to crossthe floor surface so that the power receiving electrodes oppose thepower transmitting electrodes. Thus, the arrangement of the powerreceiving electrodes is determined according to the arrangement of thepower transmitting electrodes.

With such a wireless power transmission system based on the electricfield coupling method, the capacitance between the power transmittingelectrode and the power receiving electrode opposing each other istypically small. Therefore, when transmitting a large amount of electricpower, a high voltage is applied to the power transmitting electrodes120 a and 120 b. In such a case, the intensity of the electric fieldthat leaks around the power transmitting electrodes 120 a and 120 b andthe power receiving electrodes 220 a and 220 b also becomes high.

FIG. 3 shows an example of the distribution of an electric field formedaround the power transmitting electrodes 120 a and 120 b whentransmitting power. In FIG. 3, the darker the hatching, the higher theelectric field intensity. In order to reduce the influence ofelectromagnetic noise, etc., on an electronic device, it is desirable toreduce the extent of the area of high electric field intensity that ispresent around each electrode. For example, the electric field intensityat a predetermined distance from each electrode is required not toexceed the immunity standard value determined for the electronic device.In view of biological safety, there may be a need to lower the leakageelectric field intensity aiming at the reference level determined byInternational Commission on Non-Ionizing Radiation Protection (ICNIRP).

Based on the above findings, the present inventors arrived atembodiments of the present disclosure to be described below.

An electrode unit according to one embodiment of the present disclosureis:

an electrode unit for use in a power transmitting device or a powerreceiving device of a wireless power transmission system based on anelectric field coupling method, the electrode unit including:

a first group of electrodes including a plurality of first electrodes towhich a first voltage is applied when power is transmitted; and

a second group of electrodes including a plurality of second electrodesto which a second voltage is applied when power is transmitted, whereinthe second voltage has a phase that is different from a phase of thefirst voltage by a value greater than 90 degrees and less than 270degrees, wherein:

the plurality of first electrodes and the plurality of second electrodesare arranged in a first direction along an electrode installationsurface; and

at least two of the plurality of first electrodes and at least two ofthe plurality of second electrodes are arranged alternating with eachother in the first direction.

A plurality of first electrodes and a plurality of second electrodes arearranged along a surface. The surface is referred to as the “electrodeinstallation surface”. The electrode installation surface is not limitedto a flat plane in a strict sense, but may be a curved surface. Theelectrodes do not need to be on the same plane, but it is only requiredthat they be arranged along the electrode installation surface.

Herein, “at least two of the plurality of first electrodes and at leasttwo of the plurality of second electrodes are arranged alternating witheach other in the first direction” means that these electrodes arearranged in the order of a first electrode, a second electrode, a firstelectrode and a second electrode in the first direction. That is, onesecond electrode is arranged between the two first electrodes, and onefirst electrode is arranged between the two second electrodes.

With such a configuration, when power is transmitted, the electric fieldproduced from a first electrode and the electric field produced from anadjacent second electrode are partially canceled. As a result, it ispossible to suppress the leakage electric field in a region over the gap(hereinafter referred to also as the “boundary”) between first andsecond electrodes adjacent to each other. Then, it is possible to reducethe risk of causing other nearby devices to malfunction, for example.

In one embodiment, the number of first electrodes and the number ofsecond electrodes are equal to each other. In another embodiment, thedifference between the number of first electrodes and the number ofsecond electrodes is 1. In these embodiments, all of the firstelectrodes and all of the second electrodes may be arranged alternatingwith each other. In such a case, each of the first electrodes isadjacent to one of the second electrodes and not adjacent to any of theother first electrodes. Each of the second electrodes is adjacent to oneof the first electrodes and not adjacent to any of the other secondelectrodes.

With such a configuration, the effect of suppressing the leakageelectric field described above is realized for any two adjacentelectrodes from the first group of electrodes and the second group ofelectrodes. Thus, it is possible to realize an even more pronouncedeffect.

In order to further enhance the leakage electric field suppressingeffect, the electrode unit may further include a conductor (referred toas a “third electrode”) arranged with a gap from at least one of thefirst and second groups of electrodes. The third electrode is configuredso as to have a third voltage whose amplitude is less than amplitudes ofthe first and second voltages when power is transmitted. At least aportion of the at least one third electrode may be arranged so as to belocated outside or inside the area defined by the first and secondgroups of electrodes as seen from a direction perpendicular to theelectrode installation surface.

With such a configuration, it is possible to suppress the leakageelectric field in the vicinity of (particularly, on the side of) anoutermost electrode or electrodes of the first and second groups ofelectrodes. Particularly, two third electrodes may be provided so as tobe located on opposite sides of the area defined by the first and secondgroups of electrodes as seen from a direction perpendicular to theelectrode installation surface. In such a case, it is possible to reducethe electric field intensity in the vicinity of two electrodes of thefirst and second groups of electrodes that are located at oppositesides, and it is therefore possible to realize an even more pronouncedeffect.

The electrode unit described above may include a sheet-shaped structure.The electrodes may be on the inner side of the sheet-shaped structure. Aconductor pattern formed on the substrate included in the sheet-shapedstructure may be used as the electrodes. The sheet-shaped structure maybe a layered structure including a plurality of layers, for example.With a configuration in which third electrodes are provided, at leasttwo of the first to third electrodes may be located in different ones ofthe plurality of layers. Such a configuration can be easily employedwhen a conductor (referred to as a “shield”) for suppressing the leakageelectric field is arranged in addition to the first to third electrodes,for example. Such a shield may be arranged so that the gap between afirst electrode and a second electrode, adjacent to each other, iscovered between the power transmitting device and the power receivingdevice, for example. In such a case, the shield is arranged in a layerthat is different from the first electrode and the second electrode. Thethird electrode may also be arranged in the same layer as the shield,for example. The first and second electrodes may be arranged indifferent layers.

The electrode unit set forth above may be installed on the powertransmitting device or the power receiving device of a wireless powertransmission system based on an electric field coupling method. Thepower transmitting device includes an electrode unit, and a powertransmitting circuit for supplying AC power to the first group ofelectrodes and the second group of electrodes of the electrode unit. Thepower receiving device includes an electrode unit, and a power receivingcircuit for converting AC power received by the first and secondelectrodes of the electrode unit to DC power or a different type of ACpower and supplying the converted power to a load. The wireless powertransmission system includes both of such a power transmitting deviceand such a power receiving device.

In an embodiment in which the electrode unit is installed in the powertransmitting device, the first and second groups of electrodes areconnected to the power transmitting circuit. The power transmittingcircuit includes an inverter circuit, for example. The inverter circuitoutputs AC power to be supplied to the first and second groups ofelectrodes. With the power transmitting circuit, the first voltage isapplied to the first group of electrodes and the second voltageantiphase to the first voltage is applied to the second group ofelectrodes. Herein, “antiphase” means that the phase is different by avalue greater than 90 degrees and less than 270 degrees. In oneembodiment, the difference between the phase of the first voltage andthe phase of the second voltage is set to be substantially 180 degrees.The amplitude of the second voltage is typically substantially equal tothe amplitude of the first voltage, but they may be different from eachother.

On the other hand, in an embodiment in which the electrode unit isinstalled in the power receiving device, the first and second groups ofelectrodes are connected to the power receiving circuit. The powerreceiving circuit includes a rectifier circuit or a frequency conversioncircuit, for example. The first and second groups of electrodes of thepower receiving device receive AC power from the first and second groupsof electrodes of the power transmitting device, opposing the first andsecond groups of electrodes of the power receiving device. Then, thefirst voltage is applied to the first group of electrodes of the powerreceiving device, and the second voltage antiphase to the first voltageis applied to the second group of electrodes.

Herein, an electrode unit installed in the power transmitting device maybe referred to as the “power transmitting electrode unit”, and anelectrode unit installed in the power receiving device may be referredto as the “power receiving electrode unit”. The electrodes of the powertransmitting electrode unit may be referred to as “power transmittingelectrodes”, and the electrodes of the power receiving electrode unit as“power receiving electrodes”.

In one embodiment, the number of first electrodes in the power receivingelectrode unit is equal to the number of first electrodes in the powertransmitting electrode unit, and the number of second electrodes in thepower receiving electrode unit is equal to the number of secondelectrodes in the power transmitting electrode unit. In such anembodiment, the first electrodes of the power receiving electrode unitrespectively oppose the first electrodes of the power transmittingelectrode unit when power is transmitted. Similarly, the secondelectrodes of the power receiving electrode unit respectively oppose thesecond electrodes of the power transmitting electrode unit when power istransmitted. Electric power is transmitted contactlessly via an electricfield coupling between these opposing electrodes. In order to realizeefficient power transmission, the power transmitting electrode unit andthe power receiving electrode unit may be designed with the same numberof first electrodes, the same number of second electrode, the same widthor widths of the electrodes, and the same arrangement of the electrodes.Note however that power transmission is possible even if theseparameters are not strictly equal between the power transmittingelectrode unit and the power receiving electrode unit. For example, thenumber of first electrodes in the power receiving electrode unit may bedifferent from the number of first electrodes in the power transmittingelectrode unit, and the number of second electrodes in the powerreceiving electrode unit may be different from the number of secondelectrodes in the power transmitting electrode unit. Even in such acase, it is possible to ensure a good power transmission property byappropriately designing the width of each electrode.

The power receiving device may be installed on a vehicle, for example.The “vehicle” as used herein is not limited to a vehicle such as atransport robot set forth above, but refers to any movable object thatis driven by electric power. The vehicle includes a powered vehicle thatincludes an electric motor and one or more wheels, for example. Such avehicle can be an automated guided vehicle (AGV) such as a transportrobot set forth above, a forklift, an overhead hoist transfer (OHT), anelectric car (EV), an electric cart, or an electric wheelchair, forexample. The “vehicle” as used herein also includes a movable objectthat does not include wheels. For example, the “vehicle” includes bipedwalking robots, unmanned aerial vehicles (UAVs, so-called “drones”) suchas multicopters, manned electric aircrafts, and elevators.

An electronic device according to another embodiment of the presentdisclosure is installed on a vehicle including a power receiving deviceset forth above. The power receiving device receives electric power thatis wirelessly transmitted from the power transmitting device, andsupplies the electric power to a load. The electronic device includes asensing device. The sensing device obtains information from a sensingobject around the vehicle by using electromagnetic field or ultrasonicwaves. The electronic device may further include a blocking member. Theblocking member blocks the leak electromagnetic field that occurs whenpower is transmitted from the power transmitting device to the powerreceiving device without hindering the transfer of the electromagneticfield or ultrasonic waves from the sensing object to the sensing device.The electronic device may be arranged between one of the first group ofelectrodes and one of the second group of electrodes that are adjacentto each other as seen from a direction perpendicular to the electrodeinstallation surface, for example.

The “sensing device” may be any electronic device such as an imagingdevice, a human detection sensor, an obstruction detection sensor, anRFID reader, a wireless communication device, an ultrasonic sensor, or atemperature sensor, for example. The sensing device is capable ofobtaining information from sensing objects around the vehicle by usingelectromagnetic waves such as ultraviolet rays, visible light, infraredrays, terahertz waves or microwaves, or by using electromagneticinduction. That is, the sensing device is capable of sensing the ambientenvironment by using an electromagnetic field. Other than using anelectromagnetic field, the sensing device may sense the environmentaround the vehicle by using any other physical variations such asultrasonic waves.

The “sensing object” (hereinafter referred to also as an “object”) maybe a mark including the one-dimensional or two-dimensional codedescribed above, for example. The sensing device may be an imagingdevice including a one-dimensional or two-dimensional array ofphotoelectric conversion devices, or a barcode reader. These sensors arecapable of obtaining information recorded in the code by capturing theimage of the mark. The code may include location information, forexample. In such a case, the sensing device can obtain the locationinformation of the code by reading the code. Thus, it is possible torecognize the location of the vehicle.

The “sensing object” may be a human or any other obstruction (e.g., ananimal, another vehicle, or an article temporarily placed there). Insuch a case, the sensing device may be a sensor such as a RADAR, aLIDAR, an infrared sensor, an imaging device or an ultrasonic sensor,for example. These sensors are capable of detecting the presence of ahuman or any other obstruction therearound by using electromagneticwaves or ultrasonic waves. The vehicle can perform various operationsbased on the output of the sensor. For example, when it is detected thatthere is a human or an article in the vicinity of the power transmittingelectrodes, the vehicle can instruct the power transmitting device so asto reduce or stop the power transmission.

Note that the electromagnetic field or ultrasonic waves propagating froma sensing object to the sensing device may slightly attenuate whenpassing through the blocking member. As used herein, the blocking memberallowing the majority of the energy of the electromagnetic field orultrasonic waves to pass therethrough means that “the propagation of theelectromagnetic field or ultrasonic waves is not hindered”. The functionof the present disclosure can be realized when the degree of attenuationof the energy of the electromagnetic field or ultrasonic waves to besensed is less than the degree of suppression of the electromagneticcomponent energy of the noise frequency band to be blocked.

The blocking member may completely surround the sensing device, or maypartially surround the sensing device if there is little influence ofelectromagnetic noise. The material of the blocking member may beappropriately selected based on the frequency to be used fortransmitting power and on the mode of sensing.

When the sensing device obtains information from sensing objects byusing light, the blocking member may include a transparent conductivemember. The transparent conductive member may be arranged on the path oflight entering the sensing device from sensing objects. The transparentconductive member allows light to pass therethrough, but blocks theelectromagnetic field having a relatively low frequency that is causedby power transmission. Thus, it is possible to relax the influence onthe sensing device from the electromagnetic field around each electrode,without affecting the sensing. The blocking member may surround thesensing device with the transparent conductive member and anon-transparent common conductive member.

The term “light”, as used herein, is not limited to visible light(electromagnetic waves whose wavelength is about 400 nm to about 700nm), but includes ultraviolet rays (electromagnetic waves whosewavelength is about 10 nm to about 400 nm) and infrared rays(electromagnetic waves whose wavelength is about 700 nm to about 2500nm). Ultraviolet rays may be referred to as “light in the ultravioletrange” or “ultraviolet light”, visible light may be referred to as“light in the visible range”, and infrared rays may be referred to as“light in the infrared range” or “infrared light”.

In an embodiment in which the sensing device obtains information fromsensing objects by using electromagnetic waves, the blocking member mayinclude a shield having at least one aperture therein. Such a shield maybe arranged on the path of propagation of electromagnetic waves fromsensing objects to the sensing device. At least the surface of theshield is conductive. The shield may be grounded. In such an embodiment,the sensing device obtains information from sensing objects by usingelectromagnetic waves of a band whose lowest frequency fm is higher thanthe frequency f1 of electric power to be transmitted from the powertransmitting device to the power receiving device. The diameter of eachaperture in the shield is set to a value that is greater than half thewavelength of the electromagnetic waves used for sensing and that isless than half the wavelength of the electromagnetic waves of thefrequency used for transmitting electric power. In other words, thediameter of each aperture in the shield may be set to a value that isgreater than c/(2fm) and less than c/(2f1), where c is the speed oflight in vacuum. Then, the shield can block electromagnetic waves ofrelatively low frequencies caused by power transmission while allowingto pass therethrough electromagnetic waves of relatively highfrequencies used for sensing.

A sensing object may be arranged between two power transmittingelectrodes adjacent to each other, for example. A sensing object may bea communication device, such as a mark including a one-dimensional ortwo-dimensional code or an RF tag arranged between two powertransmitting electrodes. In such a case, the blocking member may includea shield having a transparent conductive member described above or atleast one aperture on the path of electromagnetic waves such as light orradio waves extending from the mark or the communication device to thesensing device.

A sensing object may be located on one power transmitting electrodeincluded in the group of power transmitting electrodes. In such a case,a portion of a power receiving electrode that overlaps the sensingobject with the group of power transmitting electrodes and the group ofpower receiving electrodes opposing each other may be made of a lighttransmissive material. The sensing device can obtain information bydetecting light from the sensing object that has passed through thelight transmissive portion of the power receiving electrode.

Embodiments of the present disclosure will now be described in greaterdetail. Note however that unnecessarily detailed descriptions may beomitted. For example, detailed descriptions on what are well known inthe art and redundant descriptions on substantially the sameconfigurations may be omitted. This is to prevent the followingdescription from becoming unnecessarily redundant, to make it easier fora person of ordinary skill in the art to understand. Note that thepresent inventors provide the accompanying drawings and the followingdescription in order for a person of ordinary skill in the art tosufficiently understand the present disclosure, and they are notintended to limit the subject matter set forth in the claims. In thefollowing description, elements having the same function or similarfunctions are denoted by the same reference signs.

Embodiment 1

FIG. 4 is a diagram schematically showing a wireless power transmissionsystem according to Embodiment 1 of the present disclosure. In thesystem shown in FIG. 4, as opposed to the system shown in FIG. 1, thepower transmitting device includes a first group of power transmittingelectrodes including a plurality of first power transmitting electrode120 a, and a second group of power transmitting electrodes including aplurality of second power transmitting electrodes 120 b. Two first powertransmitting electrodes 120 a and two second power transmittingelectrodes 120 b are arranged alternating with each other with regularintervals therebetween in the first direction (the X direction in thisexample) along the surface of the first power transmitting electrodes120 a. The plurality of first power transmitting electrodes 120 a andthe plurality of second power transmitting electrodes 120 b extendparallel to each other along the floor surface, and are arrangedsubstantially coplanar with each other.

The power receiving device includes a first group of power receivingelectrodes including a plurality of first power receiving electrodes,and a second group of power receiving electrodes including a pluralityof second power receiving electrodes. When power is transmitted, aplurality of first power receiving electrodes respectively oppose aplurality of first power transmitting electrodes, and a plurality ofsecond power receiving electrodes respectively oppose a plurality ofsecond power transmitting electrodes. In this state, electric power iswirelessly transmitted from the power transmitting device to thetransport robot 10 including the power receiving device.

FIG. 5 is a diagram showing a general configuration of the wirelesspower transmission system shown in FIG. 4. The power transmitting device100 of the present embodiment includes a power transmitting electrodeunit 150 and the power transmitting circuit 110. The power transmittingelectrode unit 150 includes two first power transmitting electrodes 120a and two second power transmitting electrodes 120 b. The powertransmitting circuit 110 is an AC output circuit including an invertercircuit, for example. The power transmitting circuit 110 converts the DCpower supplied from a DC power supply (not shown) to AC power, andoutputs the AC power to the power transmitting electrodes 120 a and 120b.

The power transmitting circuit 110 includes two terminals for outputtingAC power. One terminal is connected to two first power transmittingelectrodes 120 a, and the other terminal is connected to two secondpower transmitting electrodes 120 b. When transmitting power, the powertransmitting circuit 110 applies a first voltage to two first powertransmitting electrodes 120 a, and applies a second voltage antiphase tothe first voltage to two second power transmitting electrodes 120 b.

The transport robot 10 includes the power receiving device 200 and aload 330. The power receiving device 200 includes a power receivingelectrode unit 250 and the power receiving circuit 210. Theconfiguration of the power receiving circuit 210 and the load 330 issimilar to that shown in FIG. 2. The power receiving electrode unit 250includes two first power receiving electrodes 220 a and two second powerreceiving electrodes 220 b. The two first power receiving electrodes 220a and the two second power receiving electrodes 220 b are arrangedalternating with each other in one direction (the X direction in FIG.4).

In the present embodiment, the width of each of the four power receivingelectrodes and the interval therebetween of the power receivingelectrode unit 250 are set to be substantially equal to those of thefour power transmitting electrodes of the power transmitting electrodeunit 150. When power is transmitted, two first power receivingelectrodes 220 a respectively oppose two first power transmittingelectrodes 120 a, and two second power receiving electrodes 220 brespectively oppose two second power transmitting electrodes 120 b. Inthis state, when AC power is output from the power transmitting circuit110, electric power is transmitted in a contactless manner via acapacitive coupling between the group of power transmitting electrodesand the group of power receiving electrodes opposing each other.

The transport robot 10 can received electric power from the powertransmitting device 100 while standing or running over the powertransmitting electrodes 120 a and 120 b. The transport robot 10 moves inthe direction in which the electrodes extend (the Y direction in FIG. 4)while keeping the power transmitting electrodes 120 a and 120 b and thepower receiving electrodes 220 a and 220 b adjacent to and opposing eachother. Thus, the transport robot 10 can move while charging a condensersuch as a capacitor, for example.

FIG. 6 is a top view schematically showing the configuration of thepower transmitting device of the present embodiment. As shown in thefigure, the power transmitting circuit 110 includes an inverter circuit(Inv). When transmitting power, the inverter circuit applies a firstvoltage to two first power transmitting electrodes 120 a, and applies asecond voltage antiphase to the first voltage to two second powertransmitting electrodes 120 b. Herein, antiphase means that the phasedifference is greater than 90 degrees and less than 270 degrees.Typically, the phase of the second voltage is 180 degrees different fromthe phase of the first voltage. Note however that electric power can betransmitted even when the phase difference is shifted from 180 degrees.The amplitude of the second voltage is substantially equal to theamplitude of the first voltage. Strictly speaking, the first and secondvoltages does not only include the component of the transmissionfrequency, but may also include components of other frequencies. In thiscase, the phase-related condition described above is satisfied for thecomponent of the transmission frequency. The term “transmissionfrequency”, as used herein, means the switching frequency of theinverter circuit connected to the power transmitting electrodes 120 aand 120 b.

Next, the effect of suppressing the leakage electric field of thepresent embodiment will be described.

FIG. 7 is a schematic cross-sectional view illustrating the effect ofsuppressing the leakage electric field according to the presentembodiment. Arrows in the figure schematically represent a part ofelectrical flux. FIG. 7 shows the moment when a positive (+) voltage isapplied to the first power transmitting electrodes 120 a and a negative(−) voltage to the second power transmitting electrodes 120 b. At othermoments, a negative (−) voltage is applied to the first powertransmitting electrodes 120 a and a positive (+) voltage to the secondpower transmitting electrodes 120 b. In FIG. 7, electrical flux linesare not drawn on the back side (the −Z side) of the power transmittingelectrodes 120 a and 120 b.

As shown in FIG. 7, in the present embodiment, two first powertransmitting electrodes 120 a and two second power transmittingelectrodes 120 b, to which a positive voltage and a negative voltage areapplied respectively at one moment, are arranged alternating with eachother in the X direction. Therefore, the electric field formed by thefirst power transmitting electrodes 120 a having a first voltage and theelectric field formed by the second power transmitting electrodes 120 bhaving a second voltage antiphase to the first voltage are partiallycanceled. As a result, this primarily reduces the intensity of theelectric field formed over the gap between the first power transmittingelectrode 120 a and the second power transmitting electrode 120 b. Thiseffect occurs similarly between any two electrodes adjacent to eachother. Therefore, in the present embodiment, as compared with a case inwhich two relatively wide power transmitting electrodes are used asshown in FIG. 1, for example, it is possible to reduce the leakageelectric field in regions that are away from the electrodes in the Zdirection.

Such an effect can be realized also when the number of first powertransmitting electrodes 120 a and the number of second powertransmitting electrodes 120 b are not two. It is only required that thenumber of at least one of the first power transmitting electrodes 120 aand the second power transmitting electrodes 120 b be two or more, andat least some of the first and second power transmitting electrodes bearranged alternating with each other. The number of first powertransmitting electrodes 120 a and the number of second powertransmitting electrodes 120 b do not need to be equal to each other.

It is possible to particularly effectively suppress the leakage electricfield when the difference between the number of first power transmittingelectrodes 120 a and the number of second power transmitting electrodes120 b is 1 or 0, and they are arranged alternating with each other.Thus, some such examples will now be described.

In the following description, Nd denotes the number of pieces into whichthe first and second power transmitting electrodes 120 a and 120 b areeach divided. The number of divisions represents the number of piecesinto which the first and second power transmitting electrodes 120 a and120 b are each divided with respect to the configuration of thereference example shown in FIG. 1. Note however that where the number offirst power transmitting electrodes 120 a and the number of second powertransmitting electrode 120 b are different from each other, the numberof divisions Nd is represented by a decimal fraction representing theaverage value therebetween. For example, when the number of first powertransmitting electrode 120 a is two and the number of second powertransmitting electrodes 120 b is three, Nd=2.5. The followingdescription primarily assumes cases in which the electrodes all have anequal length, and the total width of the first group of powertransmitting electrodes is substantially equal to the total width of thesecond group of power transmitting electrodes. As used herein,“substantially equal” is not limited to two widths being equal to eachother in a strict sense, but it falls within the definition of“substantially equal” when the difference between two widths is lessthan 10 percent of the smaller width. The lengths and the widths of theelectrodes are not limited to the following example, but may be adjustedas needed within such a range that power can be transmitted.

FIG. 8A is a top view schematically showing an example in which thepower transmitting device includes two first power transmittingelectrodes 120 a and two second power transmitting electrodes 120 b. Theconfiguration is the same as that shown in FIG. 6, where Nd=2. In thisexample, the electrodes all have an equal width and an equal length.

FIG. 8B is a top view schematically showing an example in which thepower transmitting device includes three first power transmittingelectrodes 120 a and two second power transmitting electrodes 120 btherebetween. In this example, Nd=2.5. The inner first powertransmitting electrode 120 a and the two second power transmittingelectrodes 120 b have a width that is twice the width of the outer twofirst power transmitting electrodes 120 a. At one moment, a positivevoltage is applied to the three first power transmitting electrodes 120a, and a negative voltage to the two second power transmittingelectrodes 120 b. Therefore, the electric fields formed by the threefirst power transmitting electrodes 120 a and the two second powertransmitting electrodes 120 b therebetween are partially canceled,thereby reducing the leakage electric field.

FIG. 8C is a top view schematically showing an example in which thepower transmitting device includes two first power transmittingelectrodes 120 a and two second power transmitting electrodes 120 b. Inthis example, Nd=3. The electrodes all have an equal length and an equalwidth. One or two second power transmitting electrode 120 b is arrangedadjacent to the first power transmitting electrodes 120 a. Similarly,one or two first power transmitting electrode 120 b is arranged adjacentto the second power transmitting electrodes 120 b. At one moment, apositive voltage is applied to the three first power transmittingelectrodes 120 a, and a negative voltage to the three second powertransmitting electrodes 120 b. Therefore, the electric fields formed bythe three first power transmitting electrodes 120 a and the three secondpower transmitting electrodes 120 b are partially canceled, therebyreducing the leakage electric field.

Other than the examples shown in FIG. 8A to FIG. 8C, four or more of atleast one of the first power transmitting electrodes 120 a and thesecond power transmitting electrodes 120 b may be arranged, i.e., Nd=3.5or more, for example.

In the examples described above, for the two electrodes located on theopposite sides of the group of power transmitting electrodes, there is asmall leakage electric field suppressing effect because there is noother electrodes on the outer side thereof. In order to solve thisproblem, at least one conductor may be arranged in the vicinity of atleast one of the two electrodes on the opposite sides, wherein the atleast one conductor has a voltage that is different from the voltage ofthe at least one electrode. Herein, such a conductor is referred to asthe “third electrode”, and the voltage that the third electrode has isreferred to as the third voltage.

FIG. 9 is a top view schematically showing an example of a configurationin which two third electrodes 520 are arranged on opposite sides of agroup of power transmitting electrodes. In this example, two thirdelectrodes 520 are arranged in addition to the configuration shown inFIG. 8B. The third electrodes 520 are arranged with an interval from thefirst power transmitting electrode 120 a and the second powertransmitting electrode 120 b that are located on the opposite sides.

The third electrodes 520 extend in the same direction as the directionin which the first power transmitting electrodes 120 a and the secondpower transmitting electrodes 120 b extend. The width (the dimension inthe X direction) of each third electrode 520 is smaller than the widthof each first power transmitting electrode 120 a and the width of eachsecond power transmitting electrode 120 b. The width of each thirdelectrode 520 may be very small, and may be less than 12% the width ofeach of the first and second power transmitting electrodes 120 a and 120b, for example. As seen from the direction perpendicular to a planeparallel to the first and second power transmitting electrodes 120 a and120 b, the area of each of the third electrodes 520 is less than thearea of each of the first and second power transmitting electrodes 120 aand 120 b. The area of each third electrode 520 may also be very small,and may be less than 12% the area of each of the first and second powertransmitting electrodes 120 a and 120 b, for example.

The amplitude of the third voltage that the third electrode 520 has isless than the amplitude of the first and second voltages. The term“voltage”, as used herein, means the potential with respect to thereference potential. The reference potential is typically the groundpotential.

When transmitting power, there are generally two methods to ensure thateach third electrode 520 has a voltage as described above. The firstmethod is to ground each third electrode 520 as in the example of FIG.9. The second method is to ground the two third electrodes 520 with eachother.

In the example of FIG. 9, the two third electrodes 520 are grounded. Inthis example, the two third electrodes 520 are each connected to aground terminal of the power transmitting circuit 110. When transmittingpower, an AC voltage is applied from the inverter circuit Inv of thepower transmitting circuit 110 to the power transmitting electrodes 120a and 120 b at the opposite sides. The ground potential is supplied tothe two third electrodes 520. As a result, the electrical flux generatedfrom the power transmitting electrodes 120 a and 120 b at the oppositesides are oriented with respect to the ground potential. Therefore, ascompared with a case in which there is no third electrode 520, thedistribution of the leakage electric field will rapidly converge into asmall range.

FIG. 10 is a cross-sectional view schematically showing the effect ofthe third electrodes 520. As shown in the figure, the leakage electricfields on the upper and lower surfaces of two power transmittingelectrodes 120 a and 120 b and on the side thereof are reduced via theelectromagnetic coupling between the two power transmitting electrodes120 a and 120 b at the opposite sides and the two third electrodes 520in the vicinity thereof. Thus, it is possible to reduce the malfunctionof devices not only for the direction that is perpendicular to thesurface of the group of power transmitting electrodes but also for thedirection that is parallel to the surface.

In the example of FIG. 9, the first power transmitting electrodes 120 a,the second power transmitting electrodes 120 b and the third electrodes520 extend in the same direction. The length of each third electrode 520from one end thereof that is connected to the ground terminal to theother end thereof (L shown in FIG. 9) may be set to be less than ¼ thewavelength corresponding to the frequency of the electric powertransmitted, for example. This is to prevent the third electrode 520from functioning as an antenna and giving unnecessary radiation.

FIG. 11A and FIG. 11B are each a diagram schematically showing anexample of a configuration in which two third electrodes 520 areconnected to each other. In these examples, the power transmittingelectrode unit further includes a connecting conductor 520 c thatelectrically connects together the two third electrodes 520. The thirdvoltage is supplied to the two third electrodes 520 via anelectromagnetic coupling of one third electrode 520 and a portion of theconnecting conductor 520 c with the first power transmitting electrode120 a, and an electromagnetic coupling of the other third electrode 520and another portion of the connecting conductor 520 c with the secondpower transmitting electrode 120 b.

In the example of FIG. 11A, the two third electrodes 520 extend in thesame direction as the direction in which the power transmittingelectrodes 120 a and 120 b extend. The length of the two thirdelectrodes 520 are slightly longer than that of the power transmittingelectrodes 120 a and 120 b. The connecting conductor 520 c connectstogether ends of the two third electrodes 520. The power transmittingelectrodes 120 a and 120 b are located inside the area that is definedby the two third electrodes 520 and the connecting conductor 520 c asseen from the direction perpendicular to the XY plane. Herein, the areathat is defined by the two third electrodes 520 and the connectingconductor 520 c refers to the area that is surrounded by these portions.

In the example of FIG. 11B, on the back side of the first powertransmitting electrode 120 a and the second power transmitting electrode120 b, the connecting conductor 520 c connects together portions of thetwo third electrodes 520 other than the opposite ends thereof. The term“back side” means the side opposite from the side on which the powerreceiving electrodes 220 a and 220 b are located when transmittingpower. The connecting conductor 520 c may connect together centralportions of the two third electrodes 520, as shown in the figure, or mayconnect together other portions.

With the configuration shown in FIG. 11A and FIG. 11B, when an ACvoltage is applied to the power transmitting electrodes 120 a and 120 b,a capacitive coupling occurs between the two third electrodes 520 andthe connecting conductor 520 c and the power transmitting electrodes 120a and 120 b. Specifically, a portion of the connecting conductor 520 cthat is close to the two first power transmitting electrodes 120 a andone of the third electrodes 520 are coupled with the first powertransmitting electrodes 120 a. On the other hand, a portion of theconnecting conductor 520 c that is close to the second powertransmitting electrodes 120 b and the other third electrode 520 arecoupled with the second power transmitting electrodes 120 b. Since thethird electrodes 520 are forcibly electrically connected together viathe connecting conductor 520 c, the potential thereof is forcibly fixed.As a result, the advantageous effect of the third electrode having thelow-amplitude third potential is exerted around the power transmittingelectrodes 120 a and 120 b. That is, the intensity of the leakageelectric field decreases rapidly in the X-axis direction.

With the configurations shown in FIG. 11A and FIG. 11B, the two thirdelectrodes 520 and the connecting conductor 520 c may be designed sothat the coupling capacity between the two first power transmittingelectrodes 120 a is close to the coupling capacity between the twosecond power transmitting electrodes 120 b. For example, the two thirdelectrodes 520 and the connecting conductor 520 c may be designed sothat these two coupling capacities coincide with each other. With suchconfigurations, it is possible to more effectively suppress the leakageelectric field.

The present inventors conducted an electromagnetic field analysis bothfor the configuration of the present embodiment and for theconfiguration of a reference example in which the first and second powertransmitting electrodes are not divided to test the advantageous effectsof the present embodiment. The analysis result will now be describedwith reference to FIG. 12.

In this analysis, the change of the extent of the region (referred to asthe risk region) where the electric field intensity exceeds thereference value defined by ICNIRP with respect to the number ofelectrode divisions Nd. Four different configurations shown in Table 1below were used in the analysis.

TABLE 1 Number of divisions Nd 1 (Reference example) 2 2.5 3 Width w1 of150 mm 75 mm × 2 75 mm × 1 50 mm × 3 first power 37.5 mm × 2  transmitting electrode Width w2 of 150 mm 75 mm × 2 75 mm × 2 50 mm × 3second power transmitting electrode Interelectrode 25 mm 8.3 mm 6.25 mm5 mm gap

Each configuration was set so that the total width of all the firstpower transmitting electrodes 120 a and the total width of all thesecond power transmitting electrodes 120 b are equal to each other at150 mm.

The configuration of Nd=1 corresponds to the configuration shown inFIG. 1. The width w1 of the first power transmitting electrode 120 a andthe width w2 of the second power transmitting electrode 120 b are both150 mm.

The configuration of Nd=2 corresponds to the configuration shown in FIG.8A. The width w1 of each of the two first power transmitting electrodes120 a and the width w2 of each of the two second power transmittingelectrodes 120 b are both 75 mm.

The configuration of Nd=2.5 corresponds to the configuration shown inFIG. 8B. The width of each of the two first power transmittingelectrodes 120 a at the opposite sides is 37.5 mm, and the width of eachof the first power transmitting electrode 120 a at the center and thetwo second power transmitting electrodes 120 b on the opposite sidesthereof is 75 mm.

The configuration of Nd=3 corresponds to the configuration shown in FIG.8C. The width w1 of each of the three first power transmittingelectrodes 120 a and the width w2 of each of the three second powertransmitting electrodes 120 b are both 50 mm.

For configuration, the case in which the two third electrodes 520 werearranged as shown in FIG. 9 and the case in which the two thirdelectrodes 520 were absent were analyzed. The other parameters used forthe analysis were as follows.

-   -   Length of each electrode: 450 mm    -   Input power: 1 kW    -   Width of each third electrode: 1 mm    -   Gap between two power transmitting electrodes at opposite sides        and third electrode: 0.5 mm

FIG. 12 is a graph showing the analysis result. The horizontal axisrepresents the number of divisions Nd, i.e., the four differentconfigurations. The vertical axis represents the distance from thesurface of the central portion of the group of power transmittingelectrodes to a point at which the electric field intensity becomes lessthan or equal to the reference value defined by ICNIRP. This distancecorresponds to the half value of the length of the risk region in thedirection perpendicular to the electrode surface.

As can be seen from FIG. 12, the risk region is reduced in the directionperpendicular to the electrodes with any of the configurations ascompared with the reference example where Nd=1. This effect is morepronounced for higher numbers of divisions Nd of the electrode. Theresults confirmed the effectiveness of the present embodiment in whichthe number of electrode divisions Nd is increased. Particularly, theeffect is more pronounced with configurations in which the thirdelectrodes 520 are arranged.

With the configuration shown in FIG. 8B, two of the first group ofelectrodes and the second group of electrodes that are located atopposite sides have a width smaller than that of any of the otherelectrodes. With such a configuration, as compared with a case in whichall the electrodes have the same width value, it is possible to suppressthe leakage electric field on both sides. This effect can also berealized when the width of only one of the two electrodes located atopposite sides is smaller than the width of other electrodes adjacent tothe subject electrode. In other words, the width of at least one of thetwo electrodes of the first group of electrodes and the second group ofelectrodes that are located at opposite sides may be smaller than thewidth of other electrodes adjacent to at least one of the twoelectrodes. This will now be described.

FIG. 13A is a top view schematically showing an example of aconfiguration in which the power transmitting electrodes 120 a and 120 blocated at opposite sides have a smaller width than that of powertransmitting electrodes 120 a and 120 b located on the inner side. FIG.13B is a cross-sectional view schematically showing an example of anelectric field produced from the group of power transmitting electrodesof this configuration. The configuration of FIG. 13A and FIG. 13B is aconfiguration in which the two power transmitting electrodes 120 a and120 b on the opposite sides of the configuration of FIG. 8A have asmaller width. As the width ws of the outer two power transmittingelectrodes is smaller than the width we of the inner two powertransmitting electrodes, it is possible to reduce the leakage electricfield around the outer two power transmitting electrodes.

FIG. 14A and FIG. 14B each show the change of the size of the riskregion with respect to the ws/wc ratio. FIG. 14A shows the analysisresult where third electrodes (referred to also as side grounds: SG) areabsent. FIG. 14B shows the analysis result where third electrodes arearranged on opposite sides of the group of power transmittingelectrodes. The analyses shown in FIG. 14A and FIG. 14B were conductedfor five different configurations of Nd=1, Nd=2, Nd=2.5, Nd=3 andNd=3.5. For reference, with the configuration of Nd=1, FIG. 14B alsoplots the result for the case (wo) in which third electrodes on oppositesides are absent as well as the result for the case (wSG) in which thereare third electrodes on opposite sides.

As can be seen from FIG. 14A and FIG. 14B, there is a tendency that therisk region where the leakage electric field intensity is high can bereduced by decreasing ws. Note however that when third electrodes arearranged, the effect also tends to be reduced when the ws/wc ratio isset to be too small. In view of these results, when ws/wc is greaterthan 1, the widths of the electrodes can be designed so as to satisfy0.05≤ws/wc≤0.9, for example. The effect is more pronounced if0.1≤ws/wc≤0.6 is satisfied. Note that particularly when ws is set to besmaller than wc, the number of electrode divisions may not be equalbetween the power transmitting electrode unit and the power receivingelectrode unit. As described above, reducing the width of the electrodesat opposite sides of the electrode unit tends to increase the effect ofsuppressing the risk of the electric field leakage. However, in view ofthe possibility of positional misalignment of the vehicle with the powertransmitting device, the reduction in the width of the electrodes atopposite sides may be disadvantageous for realizing a stably highcoupling capacity between the power transmitting electrode unit and thepower receiving electrode unit. In such a case, the number of electrodedivisions may be deliberately varied between the power transmittingelectrode unit and the power receiving electrode unit, and theelectrodes may be designed with appropriate widths. Then, it is possibleto increase the tolerance for the positional misalignment of the vehiclewith the power transmitting device.

FIG. 15 is a diagram schematically showing another variation of thepresent embodiment. The power transmitting electrode unit 150 in thisexample includes four first power transmitting electrodes 120 a and foursecond power transmitting electrodes 120 b. That is, in this example,Nd=4. These electrodes are arranged alternating with each other in thevertical direction (first direction) of FIG. 15, and the electrodesextend in the second direction that is orthogonal to the firstdirection. Note that it is only required that the second direction andthe first direction be crossing each other, and they do not need to beorthogonal to each other.

In the example shown in FIG. 15, the plurality of first powertransmitting electrodes 120 a are electrically connected together via afirst conductive line 120 c on one side (the left side in FIG. 15) inthe second direction of the first power transmitting electrode 120 a. Onthe other hand, the plurality of second power transmitting electrodes120 b are connected together via a second conductive line 120 d on theother side (the right side in FIG. 15) in the second direction of thesecond power transmitting electrode 120 b. The plurality of first powertransmitting electrodes 120 a are connected to one terminal of the powertransmitting circuit 110 via the first conductive line 120 c. Theplurality of second power transmitting electrodes 120 b are connected tothe other terminal of the power transmitting circuit 110 via the secondconductive line 120 d. With such a configuration, it is possible toavoid crossing between the first conductive line 120 c, to which theplurality of first power transmitting electrodes 120 a are connected,and the second conductive line 120 d, to which the plurality of secondpower transmitting electrodes 120 b are connected. Thus, the powertransmitting electrode unit 150 can be easily arranged inside the powertransmitting device.

Next, the configuration of the wireless power transmission system of thepresent embodiment that relates to power transmission will be describedin greater detail. Note that the configuration of the system to bedescribed below is an example, and may be changed as necessary dependingon the function and performance required.

FIG. 16 is a block diagram generally showing the configuration of thewireless power transmission system of the present embodiment thatrelates to power transmission. The power transmitting device 100includes the power transmitting circuit 110 for converting electricpower supplied from an external power supply 310 to AC power for powertransmission, the two first power transmitting electrodes 120 a and thetwo second power transmitting electrodes 120 b for transmitting ACpower, and a matching circuit 180 connected between the powertransmitting circuit 110 and the power transmitting electrodes 120 a and120 b. In the present embodiment, the power transmitting circuit 110 iselectrically connected to the first and second power transmittingelectrodes 120 a and 120 b via the matching circuit 180 therebetween,and outputs AC power to the first and second power transmittingelectrodes 120 a and 120 b. The transport robot 10 includes a powerreceiving device 200 and the load 330.

The power receiving device 200 includes two first power receivingelectrodes 220 a and two second power receiving electrodes 220 b to becapacitively coupled respectively to the two first power transmittingelectrodes 120 a and the two second power transmitting electrodes 120 bto receive electric power, a matching circuit 280 connected to the powerreceiving electrodes 220 a and 220 b, and the power receiving circuit210 connected to the matching circuit 280 for converting the received ACpower to DC power and outputting the DC power. The two first powerreceiving electrodes 220 a form a capacitive coupling with the two firstpower transmitting electrodes 120 a when the two first power receivingelectrodes 220 a oppose the two first power transmitting electrodes 120a. The two second power receiving electrodes 220 b form a capacitivecoupling with the two second power transmitting electrodes 120 b whenthe two second power receiving electrodes 220 b oppose the two secondpower transmitting electrodes 120 b. AC power is contactlesslytransmitted from the power transmitting device 100 to the powerreceiving device 200 via these four capacitive couplings.

There is no particular limitation on the sizes of the housing of thetransport robot 10, the power transmitting electrodes 120 a and 120 band the power receiving electrodes 220 a and 220 b in the presentembodiment, and they may be set to the following values, for example.The lengths (the sizes in the Y direction) of the power transmittingelectrodes 120 a and 120 b may be set within a range of 50 cm to 20 m,for example. The widths (the sizes in the X direction) of the powertransmitting electrodes 120 a and 120 b may be set within a range of 0.5cm to 1 m, for example. When the third electrode 520 is arranged on theside of at least one of the group of power transmitting electrodes andthe group of power receiving electrodes, the width of the thirdelectrode 520 may be set within a range of 0.5 mm to 200 mm, forexample. The size of the housing of the transport robot 10 in thedirection of travel and that in the transverse direction may each be setwithin a range of 20 cm to 5 m, for example. The lengths (the sizes inthe direction of travel) of the power receiving electrodes 220 a and 220b may be set within a range of 5 cm to 2 m, for example. The widths (thesizes in the transverse direction) of the power receiving electrodes 220a and 220 b may be set within a rage of 2 cm to 2 m, for example. Thegap between power transmitting electrodes and the gap between powerreceiving electrodes may be set within a range of 1 mm to 40 cm, forexample. Note however that the present disclosure is not limited tothese numerical ranges.

The load 330 may include a driving electric motor, a capacitor forstoring electricity or a secondary battery. The load 330 is driven orcharged by the DC power output from the power receiving circuit 210.

The electric motor may be any motor such as a DC motor, a permanentmagnet synchronous motor, an induction motor, a stepper motor and areluctance motor. The motor rotates the wheels of the transport robot 10via shafts, gears, etc., to move the transport robot 10. Depending onthe type of the motor, the power receiving circuit 210 may includevarious types of circuits such as a rectifier circuit, an invertercircuit and an inverter control circuit. In order to drive an AC motor,the power receiving circuit 210 may include a converter circuit fordirectly converting the frequency (transmission frequency) of thereceived energy (electric power) to the frequency for driving the motor.

The capacitor may be a high-capacity, low-resistance capacitor such asan electric double layer capacitor or a lithium ion capacitor, forexample. By using such a capacitor as a condenser, it is possible torealize faster charging than when a battery (secondary battery) is used.Note that a secondary battery (e.g., a lithium ion battery, etc.) may beused instead of a capacitor. In such a case, more energy can be storedalthough charging will take longer.

The transport robot 10 drives the motor using the electric power storedin a capacitor or a secondary battery to move around.

As the transport robot 10 moves, the amount of electric power stored inthe capacitor or the secondary battery (the charging amount) decreases.Therefore, recharging is needed to keep moving. In view of this, whenthe charging amount decreases below a predetermined threshold valuewhile moving, the transport robot 10 moves close to the powertransmitting device 100 for charging. The power transmitting device 100may be installed at a plurality of locations in a factory.

FIG. 17 is a circuit diagram showing a more detailed configurationexample of the wireless power transmission system. In the illustratedexample, the matching circuit 180 of the power transmitting device 100includes a series resonant circuit 130 s that is connected to the powertransmitting circuit 110, and a parallel resonant circuit 140 p that isconnected to the power transmitting electrodes 120 a and 120 b andinductively coupled to the series resonant circuit 130 s. The matchingcircuit 180 has the function of matching the impedance of the powertransmitting circuit 110 with the impedance of the power transmittingelectrodes 120 a and 120 b. The series resonant circuit 130 s of thepower transmitting device 100 has a configuration in which the firstcoil L1 and the first capacitor C1 are connected in series with eachother. The parallel resonant circuit 140 p of the power transmittingdevice 100 has a configuration in which the second coil L2 and thesecond capacitor C2 are connected in parallel to each other. The firstcoil L1 and the second coil L2 are coupled together with a predeterminedcoupling coefficient to form a transformer. The turns ratio between thefirst coil L1 and the second coil L2 is set to such a value that anintended transformer ratio (boosting ratio or step-down ratio) isrealized.

The matching circuit 280 of the power receiving device 200 includes aparallel resonant circuit 230 p that is connected to the power receivingelectrodes 220 a and 220 b, and a series resonant circuit 240 s that isconnected to the power receiving circuit 210 and inductively coupled tothe parallel resonant circuit 230 p. The matching circuit 280 has thefunction of matching the impedance of the power receiving electrodes 220a and 220 b with the impedance of the power receiving circuit 210. Theparallel resonant circuit 230 p has a configuration in which the thirdcoil L3 and the third capacitor C3 are connected in parallel to eachother. The series resonant circuit 240 s of the power receiving device200 has a configuration in which the fourth coil L4 and the fourthcapacitor C4 are connected in series with each other. The third coil L3and the fourth coil L4 are coupled together with a predeterminedcoupling coefficient to form a transformer. The turns ratio between thethird coil L3 and the fourth coil L4 is set to such a value that anintended transformer ratio is realized.

Note that the configuration of the matching circuits 180 and 280 is notlimited to that shown in FIG. 17. For example, a parallel resonantcircuit may be provided instead of each of the series resonant circuits130 s and 240 s. A series resonant circuit may be provided instead ofeach of the parallel resonant circuits 140 p and 230 p. Moreover, one orboth of the matching circuits 180 and 280 may be omitted. When thematching circuit 180 is omitted, the power transmitting circuit 110 andthe power transmitting electrodes 120 a and 120 b are connected directlyto each other. When the matching circuit 280 is omitted, the powerreceiving circuit 210 and the power receiving electrodes 220 a and 220 bare connected directly to each other. Herein, the configuration in whichthe matching circuit 180 is provided falls within the definition of aconfiguration in which the power transmitting circuit 110 and the powertransmitting electrodes 120 a and 120 b are electrically connected toeach other. Similarly, the configuration in which the matching circuit280 is provided falls within the definition of a configuration in whichthe power receiving circuit 210 and the power receiving electrodes 220 aand 220 b are electrically connected to each other.

FIG. 18A is a diagram schematically showing a configuration example ofthe power transmitting circuit 110. In this example, the powertransmitting circuit 110 includes a full bridge inverter circuitincluding four switching elements (e.g., transistors such as IGBTs orMOSFETs), and a control circuit 112. The control circuit 112 includes agate driver for outputting control signals for controlling ON(conducting) and OFF (non-conducting) of the switching elements, and aprocessor such as a microcontroller for causing the gate driver tooutput the control signals. A half bridge inverter circuit or anotheroscillation circuit such as a class E may be used instead of a fullbridge inverter circuit shown in the figure.

The power transmitting circuit 110 may include a communication modem andvarious sensors for measuring the voltage, the current, etc. When acommunication modem is provided, the data can be transmitted to thepower receiving device 200 while being superimposed over AC power. Whenthe power supply 310 is an AC power supply, the power transmittingcircuit 110 converts the input AC power into another form of AC powerhaving a different frequency or voltage.

Note that the present disclosure includes an embodiment in which a weakAC signal (e.g., a pulse signal) is transmitted to the power receivingdevice 200 not for the purpose of power transmission but for the purposeof transmitting data. Even in such an embodiment, it can be said thatweak electric power is transmitted. Therefore, transmitting a weak ACsignal (e.g., a pulse signal) also falls under the concept of “powertransmission” or “power transmission”. Also, such a weak AC signal fallsunder the concept of “AC power”.

FIG. 18B is a diagram schematically showing a configuration example ofthe power receiving circuit 210. In this example, the power receivingcircuit 210 is a full-wave rectifier circuit including a diode bridgeand a smoothing capacitor. The power receiving circuit 210 may haveanother rectifier configuration. In addition to a rectifier circuit, thepower receiving circuit 210 may include various circuits such as aconstant voltage-constant current control circuit or a communicationmodem. The power receiving circuit 210 converts the received AC energyinto a DC energy that can be used by the load 330. Various sensors formeasuring the voltage, the current, etc., output from the seriesresonant circuit 240 s may be included in the power receiving circuit210.

The coils of the resonant circuits 130 s, 140 p, 230 p and 240 s mayeach be a planar coil or a laminated coil formed on a circuit board, ora wound coil of a copper wire, a litz wire, or a twist wire, forexample. The capacitors of the resonant circuits 130 s, 140 p, 230 p and240 s may each be any type of a capacitor that has a chip shape or alead shape, for example. The capacitance between two wires with the airtherebetween may serve as these capacitors. The self-resonance propertyof each coil may be used instead of these capacitors.

The power supply 310 may be any power supply such as a commercial powersupply, a primary battery, a secondary battery, a solar battery, a fuelcell, a USB (Universal Serial Bus) power supply, a high-capacitycapacitor (e.g., an electric double layer capacitor), or a voltageconverter connected to a commercial power supply, for example. While thepower supply 310 is a DC power supply in the present embodiment, it maybe an AC power supply.

The resonant frequency f0 of each of the resonant circuits 130 s, 140 p,230 p and 240 s is typically set so as to coincide with the transmissionfrequency f1 when transmitting power. The resonant frequency f0 of eachof the resonant circuits 130 s, 140 p, 230 p and 240 s does not need tostrictly coincide with the transmission frequency f1. Each resonantfrequency f0 may be set to a value that is in the range of about 50% toabout 150% of the transmission frequency f1, for example. The frequencyf1 of power transmission may be set to 50 Hz to 300 GHz, for example, 20kHz to 10 GHz in one example, 79 kHz to 20 MHz in another example, and79 kHz to 14 MHz in still another example.

In the present embodiment, there is a gap between the power transmittingelectrodes 120 a and 120 b and the power receiving electrodes 220 a and220 b, and the distance therebetween is relatively long. The distance ofthe gap may be about 10 mm to about 200 mm, for example, and morepreferably about 10 mm to about 30 mm. Therefore, capacitances Cm1 andCm2 between the electrodes are very small, and the impedance of thepower transmitting electrodes 120 a and 120 b and the power receivingelectrodes 220 a and 220 b is very high (e.g., about several kΩ). Incontrast, the impedance of the power transmitting circuit 110 and thepower receiving circuit 210 is as low as about several Ω, for example.In the present embodiment, the parallel resonant circuits 140 p and 230p are arranged on the side closer to the power transmitting electrodes120 a and 120 b and the power receiving electrodes 220 a and 220 b,respectively, and the series resonant circuits 130 s and 240 s arearranged on the side closer to the power transmitting circuit 110 andthe power receiving circuit 210, respectively. With such aconfiguration, it is easy to match the impedance. The series resonantcircuit whose impedance becomes zero (0) at resonance is suitable formatching with an external circuit having a low input/output impedance.On the other hand, the parallel resonant circuit whose impedance becomesinfinite at resonance is suitable for matching with an external circuithaving a high input/output impedance. Therefore, it is possible toeasily realize an impedance matching by arranging the series resonantcircuits at connecting points on the side of the power supply circuithaving a low input impedance and arranging the parallel resonantcircuits at connecting points on the side of the electrode having a highoutput impedance, as in the configuration shown in FIG. 15. Similarly,it is possible to desirably realize an impedance matching of the powerreceiving device 200 by arranging the parallel resonant circuits on theelectrode side and arranging the series resonant circuits on the loadside.

Note that the impedance of the electrode is low in a configuration inwhich the distance between the power transmitting electrodes 120 a and120 b and the power receiving electrodes 220 a and 220 b is shortened ora dielectric is arranged therebetween. In such a case, it is notnecessary to employ an asymmetric resonant circuit configuration asdescribed above. When there is no impedance matching issue, the matchingcircuits 180 and 280 themselves may be omitted.

In the example shown in FIG. 16 and FIG. 17, the group of powertransmitting electrodes and the group of power receiving electrodes eachinclude four electrodes, but this is merely an example. The number ofelectrodes to be included in each of the group of power transmittingelectrodes and the group of power receiving electrodes may be changed asneeded for different applications.

With the configuration shown in FIG. 16 and FIG. 17, at least one thirdelectrode 520 may be provided in the vicinity of an outermost electrodeof at least one of the group of power transmitting electrodes and thegroup of power receiving electrodes. The third electrode 520 may bearranged inside the power receiving device 200, i.e., inside thetransport robot 10, or may be arranged on the outside of the powerreceiving device 200 or on the outside of the transport robot 10. Forexample, at least one third electrode 520 may be formed on the outsideof the housing of the power receiving device 200.

Note that it is assumed in the above description that the transportrobot 10 includes the power receiving device 200 therein, but thetransport robot 10 itself may be regarded as being a power receivingdevice. Moreover, any device that includes an “electrode unit” forreceiving power may be called a “power receiving device”. Therefore,“the housing of the power receiving device” refers not only to a housinginside the device such as the transport robot 10, but also to a housingof the device itself. At least a portion of the third electrode may bearranged on the housing of the power receiving device.

Embodiment 2

Next, an embodiment in which the transport robot 10 includes anelectronic device will be described.

Various electronic devices may be installed on the transport robot 10.For example, a sensor for detecting a movable object therearound such asa human, an animal or another vehicle may be installed. Alternatively,an electronic device such as a sensor for reading location detectingmarks arranged on the floor surface may be installed.

FIG. 19 is a diagram showing an example of a factory where a pluralityof location detecting marks 50 are arranged on the floor surface. Inthis example, the mark 50 including a two-dimensional code such as a QRcode (registered trademark), for example, is provided at a plurality oflocations on the floor surface. The transport robot 10 includes animaging device (i.e., an image sensor) for reading the mark 50 providedon the bottom surface of the housing. The two-dimensional code of themark 50 represents the coordinates of the location. By capturing theimage of the mark 50 by means of an imaging device, the transport robot10 obtains location information recorded in the mark 50. Therefore, thetransport robot 10 can recognize the location of itself.

While the mark 50 includes a two-dimensional code in this example, itmay include a one-dimensional code (e.g., a barcode). Alternatively, anRF tag may be provided instead of the mark 50. In such a case, thetransport robot 10 includes an electronic device such as an antenna anda communication device for communicating with the RF tag via radio wavesor electromagnetic induction. When an RF tag is used, it is possible toprovide more information to the transport robot 10 than when atwo-dimensional code is used.

With a mobile system as shown in FIG. 19, the transport robot 10 willpause or slow down at the position of a mark 50 for reading information.It is efficient if power can be transmitted at this point in time. Inview of this, the present inventors considered making a mobile system inwhich power can be transmitted and information can be read at the sametime.

FIG. 20 is a diagram schematically showing an example of a mobile systemin which power is transmitted and information is read at the same time.With this system, a plurality of marks 50 are arranged between two ofthe four power transmitting electrodes 120 installed on the floorsurface that are on the inner side and adjacent to each other. Animaging device is arranged on the bottom surface of the transport robot10. The imaging device reads information recorded in a mark 50 whileelectric power is being transmitted from the power transmittingelectrodes 120 a and 120 b to the power receiving electrodes 220 a and220 b.

With such a system, when a pair of power transmitting electrodes and apair of power receiving electrodes are assumedly used as shown in FIG.2, the influence of the electric field leaking into the imaging deviceis not negligible. Particularly, when a large amount of electric poweris transmitted, a high voltage is applied to the power transmittingelectrodes 120 a and 120 b. Then, the electric field leaking from thepower transmitting electrodes 120 a and 120 b and the power receivingelectrodes 220 a and 220 b into the surrounding space may become strong.As a result, the possibility of affecting the operation of the imagingdevice cannot be denied.

This problem is not limited to imaging devices, but may similarly occurto other sensing devices. For example, similar problems may occur alsowhen a sensing device such as a human detection sensor, an obstructiondetection sensor, an RFID reader, a wireless communication device or anultrasonic sensor is arranged in the vicinity of the group of powerreceiving electrodes. Electronic circuits for driving the sensing devicedescribed above and for making decisions based on the obtainedinformation may be installed on the electronic device. The interferencewith these electronic circuits is also a problem.

In the present embodiment, the power transmitting electrodes 120 a and120 b and the power receiving electrodes 220 a and 220 b are eachdivided into a plurality of portions. The electronic device is arrangedbetween two power receiving electrodes on the inner side as seen from adirection perpendicular to the electrode installation surface. With sucha configuration, it is possible to suppress the influence of theelectric field leaking into the sensing device.

FIG. 21 is a block diagram showing a basic configuration of a systemaccording to the present embodiment. In the present embodiment, inaddition to the elements shown in FIG. 5, the power receiving device 200of the transport robot 10 includes an electronic device 290 for readinginformation recorded in the mark 50. For each of the group of powertransmitting electrodes and the group of power receiving electrodes, theinterval between two electrodes on the inner side is greater than theinterval between two electrodes on the outer side. Otherwise, theconfiguration is similar to that shown in FIG. 5.

FIG. 22A is a cross-sectional view schematically showing an example of aconfiguration and an arrangement of the electronic device 290. Theelectronic device 290 of the present embodiment includes an imagingdevice 292, a control circuit 294 for controlling the imaging device292, and a conductive member 296 for accommodating an imaging device 292and the control circuit 294. Although not shown in FIG. 22A, anelectronic device 290 may include an optical system such as a lens forforming an image on a light-receiving surface 293 of the imaging device292.

The conductive member 296 includes a bottom portion supporting thecontrol circuit 294 and the imaging device 292, and a tubular sideportion. The conductive member 296 may be made of a normal conductivematerial that is not light-transmissive. The conductive member 296surrounds the imaging device 292 and the control circuit 294.

In the present embodiment, the power transmitting electrodes 120 a and120 b and the power receiving electrodes 220 a and 220 b have planarsurfaces, and are substantially parallel to the floor surface. The fourpower transmitting electrodes 120 a and 120 b are arranged on the floorsurface. The four power receiving electrodes 220 a and 220 b are locatedon the same plane that is substantially parallel to the floor surface.The mark 50, which is a sensing object, is located between two of thefour power transmitting electrodes 120 a and 120 b that are on the innerside and adjacent to each other.

As seen from a direction perpendicular to the electrodes, the center ofthe light-receiving surface 293 of the imaging device 292 is alignedwith the gap between two of the four power receiving electrodes 220 aand 220 b that are on the inner side and adjacent to each other. Thatis, the imaging device 292 is arranged so that the light-receivingsurface 293 thereof faces the floor surface without opposing any of thepower receiving electrodes 220 a and 220 b. The X coordinate of thecenter of the light-receiving surface 293 may coincide with, or may beslightly shifted from, the X coordinate of the center of the gap betweentwo of the four power receiving electrodes 220 a and 220 b that are onthe inner side and adjacent to each other. A transparent member may belocated between the light-receiving surface 293 and the floor surface.

When the imaging device 292 captures the image of a mark 50, lightenters the light-receiving surface 293 of the imaging device 292 from amark 50 that is being observed. On the other hand, the leakage electricfield, produced around the electrodes because of the power transmission,is reduced also by the third electrode 520 in addition to theadvantageous effects from electrode division. Therefore, it is possibleto reduce the influence of electromagnetic noise on the imaging device292. In the present embodiment, since the conductive member 296 isarranged, it is possible to further reduce the influence ofelectromagnetic noise on the imaging device 292.

Note that a transparent conductive member may be located between thelight-receiving surface 293 of the imaging device 292 and the floorsurface. When such a transparent conductive member is provided, it ispossible to further suppress the leakage electric field from theelectrodes.

The transparent conductive member is made of a material that islight-transmissive (i.e., that allows visible light to passtherethrough) and conductive. For example, a transparent conductivematerial such as ITO (indium tin oxide), IZO (indium zinc oxide) orPEDOT:PSS (a mixture of polythiophene and polystyrenesulfonic acid) maybe used.

The conductive member 296 may be formed from a common conductor that isnot light-transmissive. For example, any conductive material such asaluminum, iron, copper or an alloy may be used. Note that the conductivemember 296 may also be made of a transparent conductive material.

In response to an instruction from the control circuit 294, the imagingdevice 292 captures the image of the mark 50 and generates image data.From the generated image data, the control circuit 294 reads atwo-dimensional code and obtains information such as the locationindicated by the code. The obtained location information can be sent toa controller (not shown), for example, and used for controlling thetravel of the transport robot 10.

FIG. 22B is a diagram showing another example of a wireless powertransmission system including the electronic device 290. In thisexample, the two third electrodes 520 are arranged between the inner twoelectrodes 220 a and 220 b of the four power receiving electrodes 220 aand 220 b.

With such a configuration, in addition to the electric field suppressingeffect from electrode division, the suppressing effect from the thirdelectrode 520 can also be realized. Therefore, it is possible to furthersuppress the influence of electromagnetic noise on the electronic device290.

While the mark 50, which is a sensing object, is arranged between two ofthe four power transmitting electrodes 120 a and 120 b that are on theinner side and adjacent to each other in the examples shown in FIG. 22Aand FIG. 22B. The mark 50 may be arranged at any other position. Forexample, the mark 50 may be arranged between any two adjacent powertransmitting electrodes of the group of power transmitting electrodes.Depending on the position of the mark 50, the position of the electronicdevice 290 is adjusted appropriately. The mark 50 may be arranged on anyof the power transmitting electrodes 120 a and 120 b.

FIG. 23 is a cross-sectional view showing an example in which the mark50 is arranged on one of the power transmitting electrodes 120 b. FIG.24A is a diagram showing two of the four power receiving electrodes 220a and 220 b of FIG. 23 as seen from a direction perpendicular to thesurface of the power receiving electrodes 220 a and 220 b. In thisexample, the power receiving electrode 220 b that opposes the powertransmitting electrode 120 b on which the mark 50 is arranged includes atransparent region 222. With the plurality of power receiving electrodes220 a and 220 b opposing the plurality of power transmitting electrodes120 a and 120 b, respectively, the transparent region 222 is locateddirectly above the mark 50. The light-receiving surface 293 of theimaging device 292 is located so as to receive light from the mark 50having passed through the transparent region 222.

The electronic device 290 shown in FIG. 23 includes a blocking member295, which includes the conductive member 296 and a transparentconductive material 297. The conductive member 296 includes a bottomportion supporting the control circuit 294 and the imaging device 292,and a tubular side portion. The transparent conductive material 297 hasa plate-like, membrane-like or film-like structure. The transparentconductive material 297 may be called a transparent conductive plate, atransparent conductive membrane, or a transparent conductive film. Thetransparent conductive material 297 is bonded to the conductive member296. The transparent conductive material 297 and the conductive member296 surround the imaging device 292 and the control circuit 294.

When the imaging device 292 captures the image of the mark 50, thetransparent conductive material 297 is located on the path of lighttraveling from the mark 50 that is being observed toward thelight-receiving surface 293 of the imaging device 292. Therefore, lightpasses through the transparent conductive material 297 to enter theimaging device 292. On the other hand, the leakage electric field aroundthe electrodes caused by power transmission is blocked by the thirdelectrode 520, the transparent conductive material 297 and theconductive member 296. Therefore, it is possible to reduce the influenceof electromagnetic noise caused by power transmission.

The transparent region 222 may be a hole or a transparent conductivemember, for example. The transparent region 222 can be formed by cuttingout a part of the power receiving electrode 220 b. The transparentregion 222 may be formed by cutting out a part of the power receivingelectrode 220 b and filling the hole with a transparent conductivematerial. The shape and size of the transparent region 222 may be set toany shape and size as long as light from the mark 50 enters the imagingdevice 292. For example, as shown in FIG. 24B, a plurality oftransparent regions 222 may be arranged in line in the Y direction. Theentire power receiving electrode 220 b may be formed from a transparentconductive material.

A conductor having one or more apertures (referred to herein as a“shield”) may be provided instead of the transparent conductive material297. The shield may be connected to the ground (i.e., grounded). Thesize and arrangement of the apertures in the shield are set so as toallow light from the mark 50, which is a sensing object, to passtherethrough while blocking the leak electromagnetic field caused bypower transmission.

FIG. 25 is a cross-sectional view schematically showing a configurationexample in which the blocking member 295 includes a shield 298 havingone aperture 299. The shield 298 is formed from a conductive material.The aperture 299 is located on the path of light traveling from the mark50 to the imaging device 292. Light from the mark passes through theaperture 299 and a lens 291 to be detected by the imaging device 292.Note that FIG. 25 does not show power receiving electrodes other thanthe two power receiving electrodes 220 a and 220 b, of the group ofpower receiving electrodes, that are located in the middle.

The diameter of the aperture 299 is set so as to allow light from themark 50 to pass therethrough while blocking the leakage electric fieldaround the power receiving electrodes 220 a and 220 b. Specifically, thediameter of the aperture 299 may be set to a value that is less thanhalf the wavelength of the electromagnetic waves having a frequency usedfor transmitting electric power without affecting the imaging by theimaging device 292. Herein, the “diameter” of the aperture 299 means thesize of the aperture 299 in one of all the directions that are parallelto the surface of the shield 298 in which the size of the aperture 299is greatest. For example, when the shape of the aperture 299 as seenfrom above is quadrilateral, the diameter of the aperture 299 is thelength of the longer one of the diagonals. When the shape of theaperture 299 is an ellipse, the diameter of the aperture 299 is thelength of the longer axis.

When the frequency used for transmitting electric power (hereinafterreferred to as the “transmission frequency”) is 500 MHz, for example,the wavelength in the air of the electromagnetic waves having thefrequency is about 60 cm. Therefore, in such a case, the diameter of theaperture 299 may be set to be less than 30 cm. The diameter of theaperture 299 is set to an appropriate value for the transmissionfrequency. The smaller the size of the aperture 299, the lower theintensity of the electromagnetic waves passing through the aperture 299.Therefore, the size of the aperture 299 is set so that it is possible toblock the electromagnetic waves of the transmission frequency whileensuring an area needed for light used for imaging to pass therethrough.

In the example shown in FIG. 25, the shield 298 may be implemented bythe housing of the electronic device 290 or the transport robot 10. Theshield 298 may have a plurality of apertures therein.

FIG. 26 is a diagram showing another example of the shield 298. In thisexample, the shield 298 has a plurality of apertures 299 therein. Theapertures 299 are arranged in a two-dimensional array. The apertures 299may be arranged in a one-dimensional array. The apertures 299 do notneed to all have the same shape and the same size. The diameter of eachaperture 299 may be set to such a value that light from the sensingobject is allowed to pass therethrough while blocking theelectromagnetic waves of the transmission frequency.

The configuration using the shield 298 may be used for applications inwhich information is obtained from a sensing object usingelectromagnetic waves other than light. For example, it may be appliedto a system in which an RF-ID or a wireless LAN is used forcommunication. Furthermore, it may be applied to a configuration inwhich the shield 298 is used for a sensor using an ultrasonic device.

As an example, assume a case where the transmission frequency is 500kHz. With an RF-ID, if electromagnetic waves in the 900 MHz band areused, for example, these frequency bands are higher than thetransmission frequency. Also with a wireless LAN, if electromagneticwaves in the 2.4 GHz band or the 5 GHz band are used, for example, thesefrequency bands are higher than the transmission frequency. Therefore,with a shield having a plurality of apertures therein, it is possible toallow electromagnetic waves for communication to pass therethrough whilesuppressing electromagnetic noise caused by power transmission.

Similarly, with a sensing device using an ultrasonic device, it ispossible to suppress the influence of electromagnetic noise by using ashield that blocks electromagnetic waves caused by power transmissionwhile allowing ultrasonic waves pass therethrough.

With any of the configurations, the size of each aperture of the shield298 may be set so as to allow electromagnetic waves or sound waves usedfor sensing to pass therethrough without exposing the antenna or thesound wave source to the electromagnetic waves of the transmissionfrequency.

FIG. 27 is a diagram showing a variation of the configuration shown inFIG. 25. In this variation, the electronic device includes a mirror 289that reflects light from the mark 50 onto the imaging device 292. Asshown in the figure, the path of the light or electromagnetic waves froman object is not limited to a straight line, but the path may be alteredby a reflector such as the mirror 289. In this example, a transparentconductive member may be arranged instead of the shield 298 having theaperture 299.

FIG. 28 is a diagram showing another variation of the configurationshown in FIG. 25. In this variation, the shield 298 having the aperture299 is arranged between the mirror 289 and the imaging device 292. Thus,the position of the aperture 299 of the shield 298 may be any positionas long as it is on the path of light traveling from the mark 50 ontothe imaging device 292. Also in this example, a transparent conductivemember may be arranged instead of the shield 298 having the aperture299.

The configuration shown in FIG. 27 and the configuration shown in FIG.28 may be combined together. For example, a first blocking member may bearranged between the sensing object and the reflector, and a secondblocking member may be arranged between the reflector and the sensingdevice. Also in a configuration in which no reflector is provided, twoor more blocking members may be provided in series with each other. Withsuch a configuration, it is possible to further reduce the influence ofelectromagnetic noise caused by power transmission.

Next, an example of a vehicle that senses an object different from themark 50 will be described.

FIG. 29 is a diagram showing an example of the transport robot 10including a sensor for detecting humans. The transport robot 10 includesthe electronic device 290 that functions as a human detection sensor.While the position of the electronic device 290 is on the front of thetransport robot 10 in this example, the position of the electronicdevice 290 may be any position.

FIG. 30 is a diagram showing a general configuration of the electronicdevice 290. The electronic device 290 includes the imaging device 292,which is a sensing device, the conductive member 296, which functions asa housing, and the transparent conductive material 297. An opticalsystem such as a lens may be arranged between the transparent conductivematerial 297 and the imaging device 292.

In this example, when a human comes into the vicinity of the powertransmitting electrodes 120 a and 120 b while electric power istransmitted, the transport robot 10 detects the human and instructs thepower transmitting device to stop or lower the electric powertransmission. Since the conductive member 296 and the transparentconductive material 297 are provided, the influence of electromagneticnoise from the electrodes is reduced, thereby improving the humandetection precision. At least one third electrode may be provided in thevicinity of the electronic device 290. With the third electrode, it ispossible to further reduce the influence of the electric field generatedfrom the power transmitting electrodes or the power receivingelectrodes. When a sufficient electric field suppressing effect isachieved only by dividing the power transmitting electrode and the powerreceiving electrode into a plurality of portions, the transparentconductive material 297 may be omitted.

Note that the shield having one or more apertures described above may bearranged instead of the transparent conductive material 297. Aphotodetector of a different type may be arranged instead of the imagingdevice 292.

In the embodiments described above, the electrodes extend in the samedirection in parallel to each other, the present disclosure is notlimited to such a structure depending on the application. For example,the electrodes may have a rectangular shape such as a square shape. Thetechnique of the present disclosure can be applied to embodiments inwhich a plurality of such rectangular electrodes are arranged in onedirection. It is not an indispensable condition that the surfaces of allthe electrodes be on the same plane. Moreover, the surfaces of theelectrodes do not need to have a completely planar shape, but may have acurved surface or a shape with protrusions/depressions, for example.Such a surface also falls within the definition of a “planar surface” aslong as it is generally planar. The electrodes may be inclined withrespect to the road surface.

In the description set forth above, descriptions regarding the powertransmitting electrode unit can directly apply also to the powerreceiving electrode unit as long as there is no contradiction.Similarly, descriptions regarding the power receiving electrode unit candirectly apply also to the power transmitting electrode as long as thereis no contradiction.

The wireless power transmission system according to any embodiment ofthe present disclosure may be used as a system for transporting articlesinside a factory, as described above. The transport robot 10 functionsas a platform track that has a platform where articles are placed andautonomously moves around inside the factory to carry the articles tointended locations. Note however that the wireless power transmissionsystem and the vehicle of the present disclosure are not limited to suchan application, but may be used in various other applications. Forexample, the vehicle is not limited to an AGV, but may be anotherindustrial machine, a service robot, an electric car, a forklift, amulticopter (drone), an elevator, or the like. For example, the wirelesspower transmission system can be used not only in a factory, but also ina shop, in a hospital, in a house, on a road, on a runway, and in anyother place.

As described above, the present disclosure includes electrode units,power transmitting devices, power receiving devices, electronic devices,vehicles and wireless power transmission systems as set forth in itemsbelow.

[Item 1] An electrode unit for use in a power transmitting device or apower receiving device of a wireless power transmission system based onan electric field coupling method, the electrode unit including:

a first group of electrodes including a plurality of first electrodes towhich a first voltage is applied when power is transmitted; and

a second group of electrodes including a plurality of second electrodesto which a second voltage is applied when power is transmitted, whereinthe second voltage has a phase that is different from a phase of thefirst voltage by a value greater than 90 degrees and less than 270degrees, wherein:

the plurality of first electrodes and the plurality of second electrodesare arranged in a first direction along an electrode installationsurface; and

at least two of the plurality of first electrodes and at least two ofthe plurality of second electrodes are arranged alternating with eachother in the first direction.

[Item 2] The electrode unit according to item 1, wherein the number offirst electrodes and the number of second electrodes are equal to eachother, or the difference between the number of first electrodes and thenumber of second electrodes is 1.

[Item 3] The electrode unit according to item 2, wherein all of firstelectrodes and all of the second electrodes are arranged alternatingwith each other in the first direction.

[Item 4] The electrode unit according to any one of any one of items 1to 3, wherein each of the plurality of first electrodes and theplurality of second electrodes extends in a second direction along theelectrode installation surface, the second direction intersecting thefirst direction.

[Item 5] The electrode unit according to item 4, wherein:

the plurality of first electrodes are electrically connected to eachother on a first side thereof in the second direction; and

the plurality of second electrodes are electrically connected to eachother on a second side thereof, opposite to the first side, in thesecond direction.

[Item 6] The electrode unit according to any one of items 1 to 5,wherein a total width of the first group of electrodes is equal to atotal width of the second group of electrodes.

[Item 7] The electrode unit according to any one of items 1 to 6,further including:

at least one third electrode arranged with a gap from the first andsecond groups of electrodes, the at least one third electrode having athird voltage whose amplitude is less than amplitudes of the first andsecond voltages when power is transmitted,

wherein at least a portion of the at least one third electrode islocated outside an area that is defined by the first and second groupsof electrodes as seen from a direction perpendicular to the electrodeinstallation surface.

[Item 8] The electrode unit according to any one of items 1 to 7,wherein at least one of two electrodes of the first group of electrodesand the second group of electrodes that are located at opposite sideshas a width that is smaller than a width of another electrode that isadjacent to the at least one of the two electrodes.

[Item 9] The electrode unit according to any one of items 1 to 8,wherein two electrodes of the first group of electrodes and the secondgroup of electrodes that are located at opposite sides have a width thatis smaller than a width of any other electrode.

[Item 10] The electrode unit according to item 9, wherein 0.1≤ws/wc≤0.6is satisfied, where ws is a width of two electrodes of the first groupof electrodes and the second group of electrodes that are located atopposite sides, and we is a width of the other electrodes.

[Item 11] A power transmitting device including:

the electrode unit according to any one of items 1 to 10; and

a power transmitting circuit supplying AC power to the first group ofelectrodes and the second group of electrodes of the electrode unit.

[Item 12] A power receiving device including: the electrode unitaccording to any one of items 1 to 10;

a power receiving circuit for converting the AC power received by thefirst and second electrodes of the electrode unit to DC power or anotherform of AC power to supply the converted power to a load.

[Item 13] The power receiving device according to item 12, furtherincluding an electronic device including a sensing device for obtaininginformation from a sensing object around the vehicle by using anelectromagnetic field or an ultrasonic wave.

[Item 14] The power receiving device according to item 13, wherein thesensing device is located between two electrodes of the first group ofelectrodes and the second group of electrodes that are adjacent to eachother as seen from a direction perpendicular to the electrodeinstallation surface.

[Item 15] The power receiving device according to item 13 or 14, whereinthe sensing device obtains the information from the sensing object byusing light in a visible range or an infrared range.

[Item 16] The power receiving device according to item 15, wherein thesensing device is an imaging device.

[Item 17] The power receiving device according to item 16, wherein:

the sensing object is a mark including a one-dimensional or atwo-dimensional code; and

the sensing device captures an image of the mark so as to readinformation recorded in the code.

[Item 18] The power receiving device according to item 17, wherein:

the code includes location information; and

the sensing device reads the code so as to obtain the locationinformation of the code.

[Item 19] The power receiving device according to item 15 or 16,wherein:

the sensing object is a human or another obstruction; and

the sensing device detects presence of the human or the otherobstruction by using the light.

[Item 20] A vehicle including:

the power receiving device according to any one of items 12 to 19; and

a load that is driven by electric power received by the power receivingdevice.

[Item 21] A wireless power transmission system including the vehicleaccording to item 20, and the power transmitting device according toitem 11.

[Item 22] A wireless power transmission system comprising:

a power transmitting device including a power transmitting electrodeunit; and

a power receiving device including a power receiving electrode unit,wherein:

each of the power transmitting electrode unit and the power receivingelectrode unit is the electrode unit according to any one of items 1 to10;

the plurality of first electrodes of the power receiving electrode unitoppose the plurality of first electrodes of the power transmittingelectrode unit, respectively, when power is transmitted; and

the plurality of second electrodes of the power receiving electrode unitoppose the plurality of second electrodes of the power transmittingelectrode unit, respectively, when power is transmitted.

The technique of the present disclosure can be used for any device thatis driven by electric power. For example, it can be used for a vehiclesuch as an electric car (EV), an automated guided vehicle (AGV) or anunmanned aircraft (UAV).

While the present invention has been described with respect to exemplaryembodiments thereof, it will be apparent to those skilled in the artthat the disclosed invention may be modified in numerous ways and mayassume many embodiments other than those specifically described above.Accordingly, it is intended by the appended claims to cover allmodifications of the invention that fall within the true spirit andscope of the invention.

This application is based on Japanese Patent Applications No.2017-140582 filed on Jul. 20, 2017 and No. 2018-058114 filed on Mar. 26,2018, the entire contents of which are hereby incorporated by reference.

What is claimed is:
 1. An electrode unit for use in a power transmittingdevice to transfer electric power to an object that is configured to beprovided at a first position and at a second position of the powertransmitting device and includes a power receiving device to receiveelectric power from the power transmitting device at the first positionand at the second position, the electrode unit comprising: a first groupof electrodes including a plurality of first electrodes which isconfigured to be provided through the first position and the secondposition and to which a first voltage is applied when power istransmitted; and a second group of electrodes including a plurality ofsecond electrodes which is configured to be provided through the firstposition and the second position and to which a second voltage isapplied when power is transmitted, wherein the second voltage has aphase that is different from a phase of the first voltage by a valuegreater than 90 degrees and less than 270 degrees, wherein: theplurality of first electrodes and the plurality of second electrodes arearranged in a first direction along an electrode installation surface;at least two of the plurality of first electrodes and at least two ofthe plurality of second electrodes are arranged alternating with eachother in the first direction; each of the plurality of first electrodesand the plurality of second electrodes extends in a second directionalong the electrode installation surface, the second directionintersecting the first direction; and the second direction is thedirection along a line connecting the first position and the secondposition.
 2. The electrode unit according to claim 1, wherein: theplurality of first electrodes are electrically connected to each otheron a first side thereof in the second direction; and the plurality ofsecond electrodes are electrically connected to each other on a secondside thereof, opposite to the first side, in the second direction. 3.The electrode unit according to claim 1, further comprising at least onethird electrode arranged with a gap from the first and second groups ofelectrodes, the at least one third electrode having a third voltagewhose amplitude is less than amplitudes of the first and second voltageswhen power is transmitted, wherein at least a portion of the at leastone third electrode is located outside an area that is defined by thefirst and second groups of electrodes as seen from a directionperpendicular to the electrode installation surface.
 4. The electrodeunit according to claim 1, wherein at least one of two electrodes of thefirst group of electrodes and the second group of electrodes that arelocated at opposite sides has a width that is smaller than a width ofanother electrode that is adjacent to the at least one of the twoelectrodes.
 5. The electrode unit according to claim 1, wherein twoelectrodes of the first group of electrodes and the second group ofelectrodes that are located at opposite sides have a width that issmaller than a width of any other electrode.
 6. The electrode unitaccording to claim 5, wherein 0.1≤ws/wc≤0.6 is satisfied, where ws is awidth of two electrodes of the first group of electrodes and the secondgroup of electrodes that are located at opposite sides, and wc is awidth of the other electrodes.
 7. A power transmitting devicecomprising: the electrode unit according to claim 1; and a powertransmitting circuit supplying AC power to the first group of electrodesand the second group of electrodes of the electrode unit.
 8. A wirelesspower transmission system based on an electric field coupling method,comprising: a power transmitting device; and an object that isconfigured to be provided at a first position of the power transmittingdevice and at a second position of the power transmitting device and toreceive electric power from the power transmitting device; wherein thepower transmitting device comprising: an electrode unit including: afirst group of electrodes including a plurality of first electrodeswhich is configured to be provided through the first position and thesecond position and to which a first voltage is applied when power istransmitted; and a second group of electrodes including a plurality ofsecond electrodes which is configured to be provided through the firstposition and the second position and to which a second voltage isapplied when power is transmitted, wherein the second voltage has aphase that is different from a phase of the first voltage by a valuegreater than 90 degrees and less than 270 degrees, wherein: theplurality of first electrodes and the plurality of second electrodes arearranged in a first direction along an electrode installation surface;at least two of the plurality of first electrodes and at least two ofthe plurality of second electrodes are arranged alternating with eachother in the first direction; each of the plurality of first electrodesand the plurality of second electrodes extends in a second directionalong the electrode installation surface, the second directionintersecting the first direction; and the second direction is thedirection along a line connecting the first position and the secondposition; and a power transmitting circuit supplying AC power to thefirst group of electrodes and the second group of electrodes of theelectrode unit, wherein the object comprising: another electrode unitwhich is configured to receive electric power from the electrode unit ofthe power transmitting device; a power receiving circuit for convertingthe AC power received by the other electrode unit to DC power or anotherform of AC power; and a load that is driven by the electric powerconverted by the power receiving circuit.